Artificial defence structures as surrogate habitats for natural rocky shores: giving nature a helping hand (Presentation)

Student: Ally Evans
Company: Marine Ecological Solutions Ltd
Academic Supervisor: Dr Pippa Moore

Coastal Defence Structures as Surrogate Habitats for Natural Rocky Shores

Globally, coastal defence infrastructure is proliferating in the marine environment in response to sea level rise, severe weather events and increasing coastal development. In Wales, around 30% of the coast is already protected by some form of coastal defence structure, and in some parts of the world, this figure is over 50%.

In order to fulfil international marine conservation commitments, governments are prescribing a much more environmentally-sensitive approach to marine developments than previously. For example, the UK’s Marine Policy Statement advises that in addition to avoiding harm to the environment, developments should also include “beneficial features” for marine wildlife. However, much remains unknown about the potential for manmade structures to deliver ecological benefits and surrogate for natural rocky shore habitat. Our research investigates the role of coastal defences in providing substrate for marine plants and animals to colonise. It also explores the potential to manipulate structures in order to achieve more beneficial outcomes from coastal defence developments.

So far we have found that coastal defence structures tend to be poor quality habitats, supporting low biodiversity and non-natural communities. We know that rock pools are extremely important features on natural rocky shores, and are typically absent from coastal defence structures.

We therefore drilled a series of artificial rock pools into an intertidal granite breakwater to explore their potential to add some ecological benefit to the development.

Our results indicate that the rock pools have enhanced the biodiversity on the breakwater, supporting more species than the surrounding rock surfaces. But the communities living in the artificial pools are not the same as those found in natural rock pools in the surrounding area. However, the artificial pools support higher abundances of edible mussels (a species of commercial value), and of the reef-building honeycomb worm (a species of conservation importance). There is currently little understanding of what would be considered a preferred “beneficial feature” of coastal defence developments; perceived benefits may be ecological, social or economic. We will address this unanswered question via a stakeholder perception study, using a socio-economic technique called the Delphi method.

Once it is understood what ecological response is desired from coastal defence developments, it will be necessary to develop the predictive power to design structures based on the preferred outcomes. By collecting data from existing structures all around Wales, we already know what typically colonises each different type of structure. Using this data, we are building a statistical model that can predict what species will grow on new coastal defences, based on their size, shape and material, and the location in which they’re built.

We hope that the outcomes of this research will be of interest to those involved in the planning and design of new coastal defence developments, allowing them to “build-in beneficial features”, as required by our marine conservation legislation.